Christian Kerez

Circular Voids: Energy-efficient office building . Holderbank

Christian Kerez . + model pictures: © Walter Mair . © Hisao Suzuki . © Christian Kerez + © Milan Rohrer . International Holcim Awards Honorable Mention Europe 2014

This project to build a 15,000 square meter competence center includes research laboratories, office space, and generous training facilities. Perfectly circular atria cut through ceilings and floors crisscross the building, creating opportunities for employees and visitors to meet one another while also providing a sense of the building’s size from within. Inner and outer loadbearing structures of the building are mutually-dependent, voids and passive solar heating allow a climate concept with a minimal technical installation with almost no core.

One of the central points of the design is the air ventilation and climate concept, which allows through adaption of the whole system indoor climate control with almost no lines. By reducing the need for technical installation, the structure has a dramatically reduced service core. The building will fall below the requirements of the 2,000 Watt and 1t-CO2 society.
The shape of the building has an excellent ratio of surface to volume. Together with the orientation of the building, the isolated and closed façade with around 60% glass, will reduce the use of energy to a minimum and will achieve the Swiss passive housing standard (Minergie P). The circular fire escape balconies will create shading in summer when the sun is high. During winter, the elevated balconies will let the sun into the building, warming up the interior with direct sunshine. All windows and doors have efficient sun protection.
The constant temperature of the building through the whole year will be achieved by activating the mass of the building (TABS). The concrete slabs are thermally activated and keep the basic temperature of each façade, which is possible with the two different ring line systems. The air ventilation of each space can be controlled depending on needs. The spaces will be controlled depending on the outdoor air volume and the air supply.

Climate control of the whole building with high efficiency waste heat recovery (centralized and decentralized) and a heat pump with a very low flow temperature ensures that the energy requirement can be reduced to an absolute minimum. A geothermal network with a temperature of 12°C will source the energy system. Photovoltaic panels are placed on the roof with an optimal direction to the south and 35° pitch, thereby meeting a significant proportion of annual energy consumption of all technical installations and the heat pump.
The building has a very good envelope to energy reference area ratio (Ath / AE < 1.0). The primary requirements Minergie P of the building envelope are fulfilled. There will be a detailed calculation optimization of the entire energetic system. According to the guidelines, the building will be ventilated with the efficiency of the entire technology optimized in the process of design. The opaque façade is built with a U-value of 0.16-0.13 W/m2K. The roof’s thermal insulation will allow a U-value of 0.08 W/m2K. The windows are equipped with triple glazing that has an average U-value of 0.85 W/m2K.